I had 1990 might max serviced

ANONYMOUS

1990 MITSUBISHI MIGHTY MAX

150,000 MILES

I had 1990 might max serviced. Now I can't find self test dig. Conn. Under the dash.I bought the truck new and have used the self test before, Is this part easy to take off? Maybe I'm looking for it in the wrong place but i'm thinking it went missing at shop since the truck usually is locked. Any answer welcome